Rheological experiments were carried out on a 1 wt % hydrophobically modified alkali-soluble emulsion (HASE) solutions at pH similar to 9 in the presence of nonionic polyoxyethylene ether type surfactant (C12EO23). The low shear viscosity and dynamic moduli increases at c > cmc until they reach a maximum at a critical concentration, c(m) of approximately 1 mM (similar to 17 times the cme of free surfactant) and then decrease. The dominant mechanism at cmc < c < c(m) is an increase in the number of intermolecular hydrophobic junctions and a strengthening of the overall associative network structure. Above c(m), the disruption of the associative network causes a reduction in the number of junctions and strength of the overall network structure. The influence of C12EO23 on HASE before cmc could not be detected macroscopically by the rheological technique. However, isothermal titration calorimetry enables the determination of complex binding of surfactant to the polymer. Isothermal titration of C12EO23 into 0.1 wt % HASE indicates that the C12EO23 aggregation in water and 0.1 wt % HASE polymer solutions is entropically driven. A reduction in the critical aggregation concentration (cac) confirms the existence of polymer-surfactant interactions. The hydrophobic micellar junctions cause a decrease in the Delta H and Delta S of aggregation of the nonionic surfactant.